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Kernel oops noticed due to memory corruption while making management connections to the switch

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TitleKernel oops noticed due to memory corruption while making management connections to the switch
Symptoms
  • Kernel oops observed while handling TCP packet in switch.
  • The crash can be observed when attempting to login the switch via SSH, telnet, or HTTP/HTTPS continuously.
  • The issue is intermittent and random as the crash is triggered only when the memory corruption happens.
  • The following may be seen in the mini-dump output (show debug system-dump)
log: ... . Sending cookies.
log: <6>possible SYN flooding on port 23. Sending cookies.
log: <6>possible SYN flooding on port 22. Sending cookies.

 
Environment
  • EXOS < 16.1.4
Cause
This is a bug due to how EXOS handles ssh, telnet, and web servers running on multiple VRs simultaneously. If the correct sequence of events occurs when initiating a TCP connection with any of these, memory corruption can occur leading to a kernel oops crash.
Resolution
CR xos0064984 has been created to fix this issue. It will be available in the following EXOS releases:
  • EXOS 22.1.1
  • EXOS 16.2.2
  • EXOS 16.1.4
  • EXOS 21.1.2.14-patch1-2
  • EXOS 15.6.5.2-patch1-4
  • EXOS 15.3.5.2-patch1-12

As a work-around, enable ssh and/or telnet only for 1 virtual-router and disable HTTP/HTTPS.
By default ssh and telnet are enabled on all virtual-routers (vr-mgmt and vr-default).
Even if the mgmt port is not active the kernel oops can occur as ssh is enabled in that VR.
To enable ssh and telnet only on vr-default:
enable ssh2 vr vr-default
enable telnet vr vr-default

 
HTTP/HTTPS cannot be configured for only one VR. Because of this, the workaround requires that they both be disabled:
disable web http
disable web https

 
 
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